Optical transceivers, optical transponders, fiber optic transceiver modules, optoelectronic modules, and the like are commonly used to transmit and receive digital and/or analog data over fiber optic cables. These devices come in different shapes and sizes, which are a function of the operating bandwidth. Higher powered devices typically provide more bandwidth and function at higher speeds. Along with higher speeds and greater bandwidth, however, comes increasing optical transceiver power dissipation. This is important because optical transceivers have temperature operating limits that are affected by the amount of power that they dissipate.
As described above, optical transceivers, fiber optic transceiver modules, optoelectronic modules, and the like come in different shapes and sizes. That is, they have different form factors. Common form factors include C Form-Factor Pluggable (CFP), CFP2, Small Form-Factor Pluggable (SFP) enhanced Small Form-Factor Pluggable (SFP+), Quad (4-channel) Small Form-Factor Pluggable (QSFP), QSFP+, 100 Form-Factor Pluggable (CXP), 10 Form-Factor Pluggable (XFP), and the like.
The optical transceiver industry tends to be divided into two sectors. One sector is the telecommunications environment, such as telecommunication central offices. The other sector is the data communication environment, such as data centers.
In the telecommunication environment very high reliability of equipment is traditionally demanded so that if there is power outage in the telecommunication service area people can still access their telephone to call 911. As a result, there are various requirements that are called for of the equipment provided. For example, optical transceivers have to meet a fairly high operating temperature in the event of a power outage and a failure of air conditioning systems. The equipment must remain operational for up to 96 hours with an air inlet temperature of 50° C. since during a power outage the room air conditioning is no longer working, but the equipment is operating on battery back-up. This can be difficult as devices dissipate more and more power.
They also should have long term reliability. One potential obstacle to long term reliability is unfiltered air potentially entering the telecommunication equipment. Unfiltered air can allow dust to enter circuit boards in the equipment and cause shorts. As a result, in the telecommunication environment having unfiltered air potentially entering the telecommunication equipment is problematic.
In the data communication environment, the demand for reliability is not as great as it is in the telecommunication environment. The maximum operating temperature requirements are lower, 40° C. instead of 50° C., and data communication equipment does not require filtered air for cooling the system. As a result, the data communication equipment is designed a little differently. In the data communication environment, systems commonly have cool air coming in the front and warm air exiting at the back. To accomplish this, the systems have holes at the front or faceplate of the optical equipment to allow the air to enter the equipment. The air is unfiltered, however. It stands to reason that optical equipment suppliers prefer to design devices according to the less stringent demands of data communications. However, unfiltered air is unsuitable for telecommunication system operators. That is, faceplate cooling is not acceptable in telecommunication environments.
Cooling optical transceivers are becoming more troublesome in the telecommunication environment because the devices nowadays are exceeding specified operating powers in order to achieve higher speeds and higher bandwidth.
Optical device suppliers have developed cooling solutions to meet thermal requirements in data communication environments but which do not meet thermal requirements in telecommunication environments. Also, the thermal solutions tend to work for single height optical solutions as opposed to stacked optical solutions.
For example, QSFP and CXP devices are typically mounted in what is called a belly-to-belly configuration on a printed circuit board (PCB) or card. That is, some optical transceivers are mounted on the top of the PCB and some optical transceivers are on mounted on the bottom of the PCB. The optical transceiver also plugs into a receptacle, also known as a cage. There also may be a heat sink on the top of each optical transceiver. The heat sinks are meant to ride on top of the optical transceiver so that the heat sinks have a physical contact with the optical transceiver once the optical transceiver is plugged into the cage. There has been a fair bit of thermal design work with these various form factors. However, the thermal designs are all for single height cages.
Some thermal solutions have been directed towards stacked cages. Stacked cages allow for two optical transceivers to sit on top of each other. The area between the stacked cages has a latching mechanism to hold the optical transceivers in place once they are inserted into the cages. The thermal solution that has been presented to date by suppliers for stacked cages has been to punch holes in the area between the two optical transceivers. The entire cage would then sit on a PCB. This thermal solution would likely work in a data communications environment where unfiltered air entering the PCB is acceptable. However, this thermal solution is not suitable in a telecommunication environment in which unfiltered air is unacceptable.
What is needed therefore is a mechanism to keep optoelectronic devices within their temperature operating limits.
The inventive features that are characteristic of the teachings, together with further objects and advantages, are better understood from the detailed description and the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and does not limit the present teachings.